London -LRB- CNN -RRB- -- Queen Elizabeth II is to head below ground Wednesday with Prince Philip and Catherine , Duchess of Cambridge , to mark the 150th anniversary of the London Underground .

The royals are visiting central London 's Baker Street station -- a stone 's throw from the home of Sir Arthur Conan Doyle 's legendary fictional detective Sherlock Holmes at 221B Baker Street .

The queen was forced to cancel some visits last week because she was experiencing symptoms of gastroenteritis .

Once below the surface , the royal party will view a restored underground coach dating back to 1892 and talk to the people involved in bringing it back to its former glory .

They will then walk through a new S7 train , which will be officially named `` Queen Elizabeth II '' after the monarch . The royals will also meet the head of London Underground and other transport officials .

The London Underground celebrated 150 years in January since the first passengers traveled underground between Paddington and Farringdon on the Metropolitan Railway .

The Tube , as the Underground is known , is a big part of Londoners ' life , with more than 1 billion journeys made each year on its network .

The royals will also meet with representatives of the Railway Children charity , which works to help vulnerable children who live alone and at risk on the streets .

Prince William 's wife Catherine is expecting their first baby in July .

CNN 's Max Foster contributed to this report .

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The queen , Prince Philip and Catherine visit Baker Street station

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Their visit is part of celebrations to mark 150 years of the London Underground

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They will see a restored underground train carriage dating back to 1892